Effects of a decade of grazing exclusion on three Wyoming big sagebrush community types

Abstract

Livestock grazing is the most extensive land use in Wyoming big sagebrush (Artemisia tridentata ssp. wyomingensis [Beetle & A. Young] S.L. Welsh) steppe and its effects on plant community characteristics have been greatly debated. However, most of the studies used to support grazing removal evaluated the impacts of excluding historic grazing, rather than the impacts of excluding moderate contemporary grazing (40–50% utilization, altering season of use) which has vastly different effects on plant communities. Thus, to understand the effects of removing contemporary grazing, we compared contemporary grazed areas to long-term (+10 yrs.) grazing exclusion areas in three common Wyoming big sagebrush community types: intact, degraded, and exotic annual grass-dominated types. Plant community characteristics (cover, density, diversity, richness, dissimilarity) were measured in 2020 and 2021 in five grazed and grazing excluded areas within each community type. Most plant community characteristics were not influenced by grazing exclusion, suggesting that the removal of contemporary grazing has little effect on Wyoming big sagebrush plant communities. The effect of grazing exclusion on Sandberg bluegrass (Poa secunda J. Presl) abundance and litter cover varied among community types, suggesting that grazing exclusion effects slightly varied among community types. In contrast, most plant community characteristics varied among community types and between years, suggesting that grazing management plans need to account for the spatial and temporal variability among Wyoming big sagebrush communities. Furthermore, our results suggest that contemporary grazing exclusion has negligible effects compared to contemporary grazing on plant communities, and that exclusion of contemporary grazing (passive restoration) does not promote the recovery of degraded and annual grass invaded plant communities.